如何使用约束布局实现垂直链接
How to implement vertical chaining with Constraint Layout
我有一个 LinearLayout，其中每个视图填充与其权重值成比例的 space。
我有 layout_weight 8 的片段和 layout_weight 2 的 TextView。
这是下图：
使用此代码：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:tools="http://schemas.android.com/tools"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
android:orientation="vertical">
<fragment
android:id="@+id/nav_host_fragment"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="8"
app:defaultNavHost="true"
app:navGraph="@navigation/nav_graph" />
<TextView
android:id="@+id/textView2"
android:layout_width="match_parent"
android:layout_height="0dp"
android:padding="20dp"
android:layout_weight="2"
app:layout_constraintVertical_weight="2"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
tools:text="Lorem Ipsum is simply dummy text \nof the printing and typesetting industry" />
</LinearLayout>
现在将其转换为 ConstraintLayout 后，我发现很难通过使用约束链定义加权布局来复制它。
Fragment 填满屏幕，TextView 在上面，而不是分别取 layout_constraintVertical_weight = 8 和 layout_constraintVertical_weight = 2 的指定 space。
这是下图：
使用以下代码：
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:tools="http://schemas.android.com/tools"
app:layout_behavior="@string/appbar_scrolling_view_behavior">
<fragment
android:id="@+id/nav_host_fragment"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="0dp"
app:defaultNavHost="true"
app:layout_constraintVertical_chainStyle="spread"
app:layout_constraintVertical_weight="8"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:navGraph="@navigation/nav_graph" />
<TextView
android:id="@+id/textView2"
android:layout_width="match_parent"
android:layout_height="0dp"
android:padding="20dp"
app:layout_constraintVertical_weight="2"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
tools:text="Lorem Ipsum is simply dummy text \nof the printing and typesetting industry" />
</androidx.constraintlayout.widget.ConstraintLayout>
根据文档，它说 using the layout_constraintHorizontal_weight and layout_constraintVertical_weight attributes. If you're familiar with layout_weight in a linear layout, this works the same way. 它对我不起作用，或者我可能以错误的方式实施。
如何正确地将我的 LinearLayout 转换为约束布局？
要链接视图，您需要将它们绑定到另一个。在您的 xml 中，您需要将片段 app:layout_constraintBottom_toBottomOf="parent" 更改为 app:layout_constraintBottom_toTopOf="@+id/textView2" 并将 app:layout_constraintTop_toBottomOf="@id/nav_host_fragment" 添加到 TextView。
此外，我已将片段和 TextView 的 android:layout_width="match_parent" 更改为 android:layout_width="0dp"，因为使用 0dp 在约束之间传播视图是正确的。
这是解决方案。
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:tools="http://schemas.android.com/tools"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
android:orientation="vertical">
<fragment
android:id="@+id/nav_host_fragment"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="0dp"
android:layout_height="0dp"
app:defaultNavHost="true"
app:navGraph="@navigation/nav_graph"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintBottom_toTopOf="@id/textView2"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_weight="8"/>
<TextView
android:id="@+id/textView2"
android:layout_width="0dp"
android:layout_height="0dp"
android:padding="20dp"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toBottomOf="@id/nav_host_fragment"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintVertical_weight="2"
tools:text="Lorem Ipsum is simply dummy text \nof the printing and typesetting industry" />
</androidx.constraintlayout.widget.ConstraintLayout>
For fragment you are using wrong bottom constraint. fragment bottom constraint should be top of textview.
此外，您不需要使用 layout_constraintVertical_chainStyle
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior">
<fragment
android:id="@+id/nav_host_fragment"
android:layout_width="0dp"
android:layout_height="0dp"
app:defaultNavHost="true"
app:layout_constraintBottom_toTopOf="@+id/textView2"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_weight="8"
app:navGraph="@navigation/nav_graph" />
<TextView
android:id="@+id/textView2"
android:layout_width="match_parent"
android:layout_height="0dp"
android:padding="20dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintVertical_weight="2"
tools:text="Lorem Ipsum is simply dummy text \nof the printing and typesetting industry" />
</androidx.constraintlayout.widget.ConstraintLayout>
2nd way -> Also, you can do it without weight. Without layout_constraintVertical_weight you can do using guidline.
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior">
<fragment
android:id="@+id/nav_host_fragment"
android:layout_width="0dp"
android:layout_height="0dp"
app:defaultNavHost="true"
app:layout_constraintBottom_toTopOf="@+id/guideline"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:navGraph="@navigation/nav_graph" />
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_constraintGuide_percent="0.9" />
<TextView
android:id="@+id/textView2"
android:layout_width="match_parent"
android:layout_height="0dp"
android:padding="20dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/guideline"
tools:text="Lorem Ipsum is simply dummy text \nof the printing and typesetting industry" />
</androidx.constraintlayout.widget.ConstraintLayout>
我有一个 LinearLayout，其中每个视图填充与其权重值成比例的 space。
我有 layout_weight 8 的片段和 layout_weight 2 的 TextView。
这是下图：
使用此代码：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:tools="http://schemas.android.com/tools"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
android:orientation="vertical">
<fragment
android:id="@+id/nav_host_fragment"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="8"
app:defaultNavHost="true"
app:navGraph="@navigation/nav_graph" />
<TextView
android:id="@+id/textView2"
android:layout_width="match_parent"
android:layout_height="0dp"
android:padding="20dp"
android:layout_weight="2"
app:layout_constraintVertical_weight="2"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
tools:text="Lorem Ipsum is simply dummy text \nof the printing and typesetting industry" />
</LinearLayout>
现在将其转换为 ConstraintLayout 后，我发现很难通过使用约束链定义加权布局来复制它。
Fragment 填满屏幕，TextView 在上面，而不是分别取 layout_constraintVertical_weight = 8 和 layout_constraintVertical_weight = 2 的指定 space。
这是下图：
使用以下代码：
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:tools="http://schemas.android.com/tools"
app:layout_behavior="@string/appbar_scrolling_view_behavior">
<fragment
android:id="@+id/nav_host_fragment"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="0dp"
app:defaultNavHost="true"
app:layout_constraintVertical_chainStyle="spread"
app:layout_constraintVertical_weight="8"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:navGraph="@navigation/nav_graph" />
<TextView
android:id="@+id/textView2"
android:layout_width="match_parent"
android:layout_height="0dp"
android:padding="20dp"
app:layout_constraintVertical_weight="2"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
tools:text="Lorem Ipsum is simply dummy text \nof the printing and typesetting industry" />
</androidx.constraintlayout.widget.ConstraintLayout>
根据文档，它说 using the layout_constraintHorizontal_weight and layout_constraintVertical_weight attributes. If you're familiar with layout_weight in a linear layout, this works the same way. 它对我不起作用，或者我可能以错误的方式实施。
如何正确地将我的 LinearLayout 转换为约束布局？
要链接视图，您需要将它们绑定到另一个。在您的 xml 中，您需要将片段 app:layout_constraintBottom_toBottomOf="parent" 更改为 app:layout_constraintBottom_toTopOf="@+id/textView2" 并将 app:layout_constraintTop_toBottomOf="@id/nav_host_fragment" 添加到 TextView。
此外，我已将片段和 TextView 的 android:layout_width="match_parent" 更改为 android:layout_width="0dp"，因为使用 0dp 在约束之间传播视图是正确的。
这是解决方案。
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:tools="http://schemas.android.com/tools"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
android:orientation="vertical">
<fragment
android:id="@+id/nav_host_fragment"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="0dp"
android:layout_height="0dp"
app:defaultNavHost="true"
app:navGraph="@navigation/nav_graph"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintBottom_toTopOf="@id/textView2"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_weight="8"/>
<TextView
android:id="@+id/textView2"
android:layout_width="0dp"
android:layout_height="0dp"
android:padding="20dp"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toBottomOf="@id/nav_host_fragment"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintVertical_weight="2"
tools:text="Lorem Ipsum is simply dummy text \nof the printing and typesetting industry" />
</androidx.constraintlayout.widget.ConstraintLayout>
For fragment you are using wrong bottom constraint. fragment bottom constraint should be top of textview.
此外，您不需要使用 layout_constraintVertical_chainStyle
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior">
<fragment
android:id="@+id/nav_host_fragment"
android:layout_width="0dp"
android:layout_height="0dp"
app:defaultNavHost="true"
app:layout_constraintBottom_toTopOf="@+id/textView2"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_weight="8"
app:navGraph="@navigation/nav_graph" />
<TextView
android:id="@+id/textView2"
android:layout_width="match_parent"
android:layout_height="0dp"
android:padding="20dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintVertical_weight="2"
tools:text="Lorem Ipsum is simply dummy text \nof the printing and typesetting industry" />
</androidx.constraintlayout.widget.ConstraintLayout>
2nd way -> Also, you can do it without weight. Without layout_constraintVertical_weight you can do using guidline.
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior">
<fragment
android:id="@+id/nav_host_fragment"
android:layout_width="0dp"
android:layout_height="0dp"
app:defaultNavHost="true"
app:layout_constraintBottom_toTopOf="@+id/guideline"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:navGraph="@navigation/nav_graph" />
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_constraintGuide_percent="0.9" />
<TextView
android:id="@+id/textView2"
android:layout_width="match_parent"
android:layout_height="0dp"
android:padding="20dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/guideline"
tools:text="Lorem Ipsum is simply dummy text \nof the printing and typesetting industry" />
</androidx.constraintlayout.widget.ConstraintLayout>